Field of the Invention:
The present invention relates to an ultraviolet curable resin composition for forming a self-lubricating liner of a sliding member such as an unlubricated sliding bearing and a reamer bolt, a sliding member provided with the self-lubricating liner, and a manufacturing method for producing the sliding member.
Description of the Related Art:
A sliding bearing in which a shaft of rotary motion or translational motion is held by a sliding surface has been widely used. In particular, an unlubricated sliding bearing using no lubricating oil for a sliding surface has been used for applications requiring low friction coefficient, high durability, high load capacity, high heat resistance, high oil resistance, and the like, such as vessel or ship application and aircraft application.
As the unlubricated sliding bearing, Japanese Patent Application Laid-open No. 2007-255712 discloses a spherical bearing for high-load application including an outer race member having a concave first bearing surface and an inner race member having a convex second bearing surface slidably movable relative to the first bearing surface. In the spherical bearing, one of the outer race member and the inner race member is made of titanium alloy which has a bearing surface made of titanium nitride formed on the titanium alloy surface by a physical vapor deposition method (PVD). The bearing surface of the other member includes a self-lubricating liner made from resin. The self-lubricating liner is composed of a fabric including fibers of polytetrafluoroethylene (PTFE) and polyaramid. The fabric is saturated with a phenol resin composition.
U.S. Pat. No. 6,180,574 discloses a self-lubricating coating composed of a thermosetting acrylic composition in which dipentaerythritol pentaacrylate is contained in an amount of 20% by weight or more and a solid lubricant such as polytetrafluoroethylene is contained in an amount of 10% by weight or more with respect to the total amount of the thermosetting acrylic composition. 20% by weight or more of triethylene glycol dimethacrylate and 1% by weight or less of aramid pulp may be added to the self-lubricating coating. U.S. Pat. No. 6,180,574 also discloses a sleeve bearing in which the self-lubricating coating is applied, as a liner, on the inner circumferential surface of an outer race.
Japanese Patent Application Laid-open No. 2011-247408 filed by the applicant of the present application discloses a sliding bearing suitable for the aircraft application and the like. The sliding bearing includes a self-lubricating liner formed on a sliding surface of the sliding bearing, and the self-lubricating liner is composed of a self-lubricating resin composition obtained by mixing 60% by weight to 80% by weight of polyether ketone resin, 10% by weight to 30% by weight of PTFE, 5% by weight to 15% by weight of carbon fiber, and 15% by weight or less of aramid fiber. The total amount of the carbon fiber and the aramid fiber is 10% by weight to 25% by weight in the self-lubricating resin composition. A metal surface on which the self-lubricating liner is formed has a surface roughness Ra (average centerline roughness) of 4.0 μm or more and an Rmax (maximum height) of 30.0 μm or more.
The unlubricated sliding bearings disclosed in Japanese Patent Application Laid-open No. 2007-255712, U.S. Pat. No. 6,180,574 and Japanese Patent Application Laid-open No. 2011-247408 are used by being incorporated into the aircraft and the like, and thus they are required to have low friction coefficient, high load capacity, heat resistance, oil resistance, and the like. Further, there is a demand from airframe manufacturers such that a fitting adjustment can be performed by adjusting the size of a sliding surface of a sliding bearing through grinding or cutting in an assembling step of the sliding bearing such as the sleeve bearing, instead of performing the size adjustment of a shaft.
However, in the case of the fibrous lubricating liner described in Japanese Patent Application Laid-open No. 2007-255712, it is not possible to perform the size adjustment through the grinding or the cutting because, if it is subjected to such a posterior processing, the fibers of the lubricating liner will be cut and the lubricating liner will not function as a liner any longer.
The self-lubricating coating described in U.S. Pat. No. 6,180,574 is based on thermosetting acrylic resin, and thus it takes time to cure. This brings such a problem that the productivity thereof is low. Further, if an attempt is made to handle the thermosetting acrylic resin in an uncured condition in order to save time, the uncured resin flows and the shape of self-lubricating coating cannot be maintained. Thus, it is difficult to handle the self-lubricating coating based on the thermosetting acrylic resin.
The self-lubricating liner described in Japanese Patent Application Laid-open No. 2011-247408 is based on the polyether ketone resin which is thermoplastic resin, and thus the self-lubricating liner can be produced by an injection molding method achieving high productivity. However, in order to improve the adhesion of the liner to the inner circumferential surface of the outer race, it is required that a shot blasting process for roughening the surface roughness of the inner circumferential surface of the outer race be performed beforehand. Further, in a case that PTFE is blended as a solid lubricant with the thermoplastic resin such as the polyether ketone resin, PTFE is required to be blended in an amount of less than 30% by weight with respect to the total amount of the thermoplastic resin. The reason thereof is as follows. During the kneading of resin and the injection molding, PTFE generates decomposition gas because it is heated to its melting point or more by being exposed to high temperature and high pressure. From the viewpoint of safety, it is required that such decomposition gas be prevented from being generated. Accordingly, the addition amount of PTFE should be limited. On the other hand, in order to improve the lubricating property of the liner, it is desirable that the addition amount of PTFE be increased.
Under the above circumstances, there is a demand for a resin composition for a self-lubricating liner which can ensure a sufficient addition amount of PTFE, can be handled easily during manufacturing steps, and requires no process for roughening the base surface.